Instructions
Left-click the region where you are currently recruiting units.
Click the "Recruit" tab.
Right-click all of the units being recruited. Large icons beneath the recruitment options represent each unit you are currently recruiting. Right-clicking these removes them from the queue.
Click the city from which you want to recruit units. Click the "Recruit" tab.
Right-click any of the units under the recruitment options. This adds them to the queue, and the units produced will start at that city.